1. Field of the Invention
The present invention relates to a modular construction of a power circuit and converter transformer of a switching power supply unit.
2. Description of the Prior Art
In recent years, the development of smaller and lighter low power systems has been progressing remarkably to meet the demand for smaller electronic equipment. As for high power systems, however, particularly power circuits, reduction in size and weight has not yet been realized.
In fact, the mounting technology developed for low power systems is virtually useless for high power systems, due to heat radiation from high power devices and the constructional requirement that high power devices be placed close to one another. Accordingly, in view of the electrical separation between primary and secondary circuits and the heat radiation requirement, a large heat sink is mounted on each semiconductor device of a power system, as a method employed at present.
The integrated module disclosed in Japanese Laid-Open Patent Application No. 44-21621 (U.S. Pat. No. 3,359,461) has provided a solution to the conventional problems. This module comprises power devices and a converter transformer housed in a hollow prism container surrounded by electroconductive side walls. However, the module has the following problems:
(1) It involves many assembly processes because of its complicated structure.
(2) Since the entire module is electroconductive, insulation from surrounding structures is difficult.
(3) The converter transformer in the module is susceptible to heat radiation from surrounding power devices.
(4) Since the power devices are mounted on the side walls, electrical separation between the primary and secondary circuits, essential in power equipment, is difficult.
In short, defective spatial layout of primary and secondary circuits and converter transformers has resulted in the above problems.